Address review feedback on cortex-m run.sh wiring

Drops `--quantize` from .ci/scripts/test_cortex_m_e2e.sh — run.sh has no
such flag (only --no_quantize), so it was being silently swallowed; the
default behavior is to quantize, so the wrapper just needs to omit it.

Moves the dummy-input file creation back into run_fvp.sh so the script
is self-contained when given --bundle=. Previously run.sh created
fvp_dummy_input.bin next to the .bpte and run_fvp.sh asserted its
existence — a cross-script contract enforced only by ordering. With this
change run_fvp.sh creates the placeholder itself; future callers of
run_fvp.sh --bundle= no longer need to know about the requirement.

Adds a cortex-m branch to run.sh's check_setup() so a missing
arm-none-eabi-gcc toolchain surfaces immediately rather than deeper in
the build_test_runner.sh chain.

Adds a comment to run_fvp.sh's FVP-model selection noting that
cortex-m55 specifically maps to the SSE-300 FVP because it's the only
Cortex-M CPU on Corstone-300 today; cortex-m85 falls through to SSE-320.

Removes the now-redundant `backends/cortex_m/test/build_test_runner.sh`
step from the reusable cortex-m e2e workflow — run.sh invokes it
internally as part of the cortex-m target branch.

This change was authored with Claude (claude-opus-4-7[1m]).

Author: rascani

.ci/scripts/test_cortex_m_e2e.sh

@@ -17,8 +17,9 @@ MODEL=$1
 script_dir=$(realpath "$(dirname "${BASH_SOURCE[0]}")")
 et_root_dir=$(realpath "${script_dir}/../..")
 
+# Quantization is the default for the cortex-m55+int8 target; run.sh's
+# arg parser only recognizes --no_quantize, so we omit any explicit flag.
 bash "${et_root_dir}/examples/arm/run.sh" \
     --model_name="${MODEL}" \
     --target=cortex-m55+int8 \
-    --quantize \
     --bundleio

.github/workflows/_test_cortex_m_e2e.yml

@@ -43,8 +43,5 @@ jobs:
         .ci/scripts/setup-arm-baremetal-tools.sh
         source examples/arm/arm-scratch/setup_path.sh
 
-        # Build cortex-m test runner with bundled IO support
-        backends/cortex_m/test/build_test_runner.sh
-
-        # Export model and run on FVP
+        # Export and run model on FVP (run.sh internally builds the test runner).
         bash .ci/scripts/test_cortex_m_e2e.sh ${{ matrix.model }}

backends/arm/scripts/run_fvp.sh

@@ -55,6 +55,8 @@ done
 
 elf_file=$(realpath ${elf_file})
 
+# cortex-m55 is the only Cortex-M CPU on the Corstone-300 board today;
+# cortex-m85 lives on Corstone-320, so it falls through to the SSE-320 FVP.
 if [[ ${target} == *"ethos-u55"* || ${target} == cortex-m55* ]]; then
     fvp_model=FVP_Corstone_SSE-300_Ethos-U55
 else
@@ -111,11 +113,9 @@ if [[ ${target} == cortex-m* ]]; then
     bundle_file=$(realpath "${bundle_file}")
     bundle_dir=$(dirname "${bundle_file}")
     bundle_name=$(basename "${bundle_file}")
-    # The bundled-IO runner requires its -i argument to refer to a real file
-    # even though inputs come from the embedded bundle; the caller is expected
-    # to have created fvp_dummy_input.bin next to the bundle.
-    [[ ! -f "${bundle_dir}/fvp_dummy_input.bin" ]] \
-        && { echo "[${BASH_SOURCE[0]}] ${bundle_dir}/fvp_dummy_input.bin is missing; the caller must create a placeholder input file next to the bundle"; exit 1; }
+    # Bundled-IO runner needs -i to point at a real file even though
+    # inputs come from the bundle.
+    dd if=/dev/zero of="${bundle_dir}/fvp_dummy_input.bin" bs=4 count=1 2>/dev/null
     ${nobuf} ${fvp_model}                                              \
         -C ethosu.num_macs=${num_macs}                                 \
         -C mps3_board.visualisation.disable-visualisation=1            \

examples/arm/run.sh

@@ -223,6 +223,10 @@ function check_setup () {
             || { echo "Executorch repo doesn't contain CMakeLists.txt file at root level"; return 1; }
 
     backends/arm/scripts/build_executorch.sh --et_build_root="${et_build_root}" --build_type=$build_type $devtools_flag $et_dump_flag --toolchain="${toolchain}"
+    elif [[ ${target} == cortex-m* ]]; then
+        # build_test_runner.sh handles toolchain setup; just validate it's on PATH.
+        hash arm-none-eabi-gcc \
+            || { echo "Could not find arm-none-eabi-gcc on PATH, ${_setup_msg}"; return 1; }
     elif [[ ${target} =~ "vgf" ]]; then
         model_converter=$(which model-converter)
         echo "${model_converter}"
@@ -364,10 +368,6 @@ for i in "${!test_model[@]}"; do
         set -x
         backends/cortex_m/test/build_test_runner.sh
         cortex_m_elf="${et_root_dir}/arm_test/arm_semihosting_executor_runner_corstone-300/arm_executor_runner"
-        # The bundled-IO runner requires its -i argument to point at a real file
-        # even though inputs come from the bundle; write a placeholder next to
-        # the .bpte for run_fvp.sh to pass along.
-        dd if=/dev/zero of="$(dirname "${pte_file}")/fvp_dummy_input.bin" bs=4 count=1 2>/dev/null
         if [ "$build_only" = false ] ; then
             backends/arm/scripts/run_fvp.sh --elf="${cortex_m_elf}" --target="${target}" --bundle="${pte_file}"
         fi